Unit Conversion Question
I didn't check the math, but it looks like you are on the right track.
Remember what I said about carrying along units in your equations, though. Even if you don't show the units while you type here on the forum, hopefully you are now showing units for each of the quantites in the equations that have them, and cancelling them out when they appear on top and bottom like cm/cm = 1, so cross them both out. That will save you many, many errors over the years, and also help you figure out what goes on the top and bottom of a fraction when you aren't sure.
Like, what is the relationship between wavelength, speed and frequency? Well, if wavelength's units are m, speed is m/s, and frequency is 1/s (=Hz), then you can figure out the equation just based on keeping the units consistent, right?